The refractive index (RI) of a material—that is, the ratio of the speed of light in a vacuum to the speed of light in the material—can be an important property for use in species identification and material characterization. For example, in industries such as food production and pharmaceuticals, RI can be used as a measure of product quality or to characterize reactions and other dynamic processes. More specifically, precise species identification can be achieved using multi-wavelength RI measurement, and the ability to perform real-time or continuous multi-wavelength RI measurements can be useful for monitoring the properties of analytes and other chemical constituents.
Conventional refractometers and techniques for measuring RI have various drawbacks and limitations. For example, conventional refractometers use single wavelength sources or filtered light and are capable of measuring RI only for discrete wavelengths. Multi-wavelength measurement requires moving parts (e.g., rotation of the sample and/or prism(s)) or serial measurements. Consequently, such refractometers have limited ability to observe RI in real-time and to produce continuous dispersion profiles. Thus, new techniques for RI measurements are still needed.